Simultaneous multislice diffusion-weighted imaging versus standard diffusion-weighted imaging in whole-body PET/MRI.

OBJECTIVE: To compare standard (STD-DWI) single-shot echo-planar imaging DWI and simultaneous multislice (SMS) DWI during whole-body positron emission tomography (PET)/MRI regarding acquisition time, image quality, and lesion detection. METHODS: Eighty-three adults (47 females, 57%), median age of 64 years (IQR 52-71), were prospectively enrolled from August 2018 to March 2020. Inclusion criteria were (a) abdominal or pelvic tumors and (b) PET/MRI referral from a clinician. Patients were excluded if whole-body acquisition of STD-DWI and SMS-DWI sequences was not completed. The evaluated sequences were axial STD-DWI at b-values 50-400-800 s/mm2 and the apparent diffusion coefficient (ADC), and axial SMS-DWI at b-values 50-300-800 s/mm2 and ADC, acquired with a 3-T PET/MRI scanner. Three radiologists rated each sequence's quality on a five-point scale. Lesion detection was quantified using the anatomic MRI sequences and PET as the reference standard. Regression models were constructed to quantify the association between all imaging outcomes/scores and sequence type. RESULTS: The median whole-body STD-DWI acquisition time was 14.8 min (IQR 14.1-16.0) versus 7.0 min (IQR 6.7-7.2) for whole-body SMS-DWI, p < 0.001. SMS-DWI image quality scores were higher than STD-DWI in the abdomen (OR 5.31, 95% CI 2.76-10.22, p < 0.001), but lower in the cervicothoracic junction (OR 0.21, 95% CI 0.10-0.43, p < 0.001). There was no significant difference in the chest, mediastinum, pelvis, and rectum. STD-DWI detected 276/352 (78%) lesions while SMS-DWI located 296/352 (84%, OR 1.46, 95% CI 1.02-2.07, p = 0.038). CONCLUSIONS: In cancer staging and restaging, SMS-DWI abbreviates acquisition while maintaining or improving the diagnostic yield in most anatomic regions. KEY POINTS: • Simultaneous multislice diffusion-weighted imaging enables faster whole-body image acquisition. • Simultaneous multislice diffusion-weighted imaging maintains or improves image quality when compared to single-shot echo-planar diffusion-weighted imaging in most anatomical regions. • Simultaneous multislice diffusion-weighted imaging leads to superior lesion detection.

Clinical utility of a postprocedural CT scan in CT-guided musculoskeletal biopsies.

OBJECTIVE: The purpose of this study is first to determine the clinical utility of the postprocedure scan in detecting postinterventional complications after CT-guided musculoskeletal biopsies, and second to evaluate the contribution to the radiation dose of the postprocedural CT scan. MATERIALS AND METHODS: Retrospective analysis of 500 consecutive CT-guided musculoskeletal biopsies over an 18-month period from 29 March 2017 to 28 September 2018, where spiral postprocedure scans were obtained in every case. To assess the clinical utility of postinterventional CT scans, it was determined whether immediate post-procedural complications were detected on the postprocedural scans only or were also seen on the procedural images. To evaluate the relative radiation exposure of postprocedural scans, a ratio was obtained of the dose-length product (DLP) of the postprocedural scan compared with the total DLP of each case. RESULTS: A total of 397 bone biopsies and 103 soft-tissue biopsies were performed in 471 patients. The immediate postprocedural complication rate was 0.4% (2 out of 500) in all procedures. Both complications were minor (small hematomas) and detected only on postinterventional CT scans. The average total DLP for the procedures was 383.5 mGy*cm. The average DLP of the postprocedural scan was 64.0 mGy*cm. The average radiation dose contribution of the postprocedural CT scans toward the total DLP was 17.4%. CONCLUSION: Immediate postprocedural complications in CT-guided musculoskeletal interventions are rare. When complications do occur, they are usually minor. To substantially reduce radiation dose, postinterventional CT scans should not be performed routinely.

Imaging findings during and after percutaneous cryoablation of hepatic tumors.

OBJECTIVE: Imaging plays a key role in the assessment of patients before, during, and after percutaneous cryoablation of hepatic tumors. Intra-procedural and early post-procedure imaging with CT and MRI is vital to the assessment of technical success including adequacy of ablation zone coverage. Recognition of the normal expected post-procedure findings of hepatic cryoablation such as ice ball formation, hydrodissection, and the normal appearance of the ablation zone is crucial to be able to differentiate from complications including vascular, biliary, or non-target organ injury. Delayed imaging is essential for determination of clinical effectiveness and detection of unexpected findings such as residual unablated tumor and local tumor progression. The purpose of this article is to review the spectrum of expected and unexpected imaging findings that may occur during or after percutaneous cryoablation of hepatic tumors. CONCLUSION: Differentiating expected from unexpected findings during and after hepatic cryoablation helps radiologists identify residual or recurrent tumor and detect procedure-related complications.

Multimodality Imaging, including Dual-Energy CT, in the Evaluation of Gallbladder Disease.

Imaging of the gallbladder has a key role in the examination of patients with abdominal pain-especially pain localized to the right upper quadrant. Pathologic conditions that affect the gallbladder include cholelithiasis and associated complications such as acute and chronic cholecystitis, choledocholithiasis, gallstone pancreatitis, and cancer. Modalities used to image the gallbladder include ultrasonography (US), computed tomography (CT), magnetic resonance (MR) imaging, and nuclear scintigraphy. US is the primary imaging modality used to evaluate entities suspected of being gallbladder disease, as it is both sensitive and specific for demonstrating gallstones, biliary duct dilatation, and inflammatory features. However, CT is often the first imaging examination performed in patients who present to the emergency department with acute abdominal pain. Because the CT appearance of gallstones is variable, depending on the composition of the stone, pattern of calcification, and presence of gas, gallstones and other gallbladder conditions can be difficult to detect at conventional multidetector CT, with which data are acquired by using a single x-ray energy spectrum. Dual-energy CT, with which one takes advantage of the material-dependent x-ray absorption behavior of concurrently acquired high- and low-kilovolt-peak data, can add value by increasing the conspicuity of noncalcified gallstones and improving the detection of acute cholecystitis and gallbladder malignancy. In addition, MR cholangiopancreatography can be helpful for assessing choledocholithiasis and complicated biliary duct disease. ©RSNA, 2018.

Cystic mediastinal masses and the role of MRI.

While some cystic masses can be definitively diagnosed on CT, others remain indeterminate. Because of its intrinsic superior soft tissue resolution, MR is an important tool in the evaluation of select mediastinal masses that are incompletely characterized on CT. This review describes how non-vascular MR provides greater diagnostic precision in the evaluation of indeterminate cystic mediastinal masses on CT. It also emphasizes key MR pulse sequences for optimal evaluation of problematic mediastinal masses.

Cancer Yield of Incidental Breast Lesions Detected on Chest Computed Tomography.

OBJECTIVE: This study aimed to determine the cancer yield for abnormal breast findings initially identified on chest computed tomography (CT). MATERIALS AND METHODS: This institutional review board-approved, Health Insurance Portability and Accountability Act-compliant study retrospectively reviewed reports of 41,217 consecutive chest CT examinations done from January 1, 2006, to December 31, 2011, to identify those with breast findings noted in the impression of the report. Examinations done for staging of newly diagnosed breast cancer were excluded. The electronic medical record was searched for any subsequent breast imaging and any corresponding pathology results. Cancer yield was calculated. RESULTS: A total of 258 chest CT examinations with abnormal breast findings were identified in 218 unique patients. Average patient age was 65.6 years (range, 30-100 years). There were 207 women and 11 men. Of these, 75 patients had follow-up breast imaging in our system. One hundred forty-three patients did not have follow-up in our system and were excluded for purposes of cancer detection rate calculation. Thirteen of 75 patients were found to have lesions that were malignant: infiltrating ductal carcinoma (8), invasive lobular carcinoma (2), lymphoma (2), and intracystic papillary cancer with atypical features (1). Four of 75 patients underwent further workup and were found to have lesions that were benign: fibroadenoma (3) and benign fibrocystic change (1). The remainder of the 58 of 75 patients had dedicated breast imaging that was classified as either Breast Imaging Reporting and Data System score 1 or 2, and no further workup was performed. Cancer yield from CT findings was 17.3%. CONCLUSIONS: Abnormal CT findings in the breast warrant additional evaluation with dedicated breast imaging to evaluate for a possible underlying malignancy. Cancer yield from CT findings in this study was 17.3%.